1. Field of the Invention
This invention relates to polyesters containing acryloyl groups which can be converted into crosslinked products by radiation curing and to a process for their production.
2. Description of the Prior Art
It is known that polyesters containing at least 2 acryloyl groups can be crosslinked by radiation curing (electron beam or UV curing). These polyester acrylates, which are obtained in the form of reaction products of acrylic acid with diols, polyols and dicarboxylic acids (as described for example in DE-OS Nos. 2 261 612 or 2 838 691), generally have a highly viscous, partly resin-like consistency. In order to process these compositions, large quantities of vinyl monomers, so-called reactive diluents, have to be added.
In most cases, however, the effect of using reactive diluents is that, in the formulations to be applied, the binder is very heavily diluted so that the paint properties produced by the polyester acrylates are offset by the reactive diluents incorporated into the film by polymerization. This effect is observed particularly clearly when the binder has a highly viscous consistency. In addition, many vinyl monomers have a strong natural odor and an irritating effect on the skin.
It is known (cf. for example DE-OS No. 3 704 098) that low viscosity polyester acrylates may be obtained by esterifying low molecular weight polyesters or polyethers are esterified. However, coating compositions based on these starting materials are attended in particular by the disadvantage of comparatively slow curing under irradiation.
Accordingly, an object of the present invention is to provide new polyester acrylates which, by virtue of their low viscosity, require very little solvent for attaining application viscosity and which, after radiation curing, possess the known favorable properties of polyester acrylates.
It has now surprisingly been found that this objective may be achieved using the polyester acrylates according to the invention which are described in detail hereinafter.